Method of manufacturing chip inductor

ABSTRACT

Manufacturing method of the present invention comprises the steps of a conductive layer forming process for forming conductive layer  4  on outer periphery  2  and end surfaces  3  of substrate  1,  a coil portion forming process for forming coil portion  7  having conductor  5  and groove  6  by cutting spirally the conductive layer  4,  an etching process for etching the substrate  1  having the coil portion  7  formed thereon; an insulation resin coating process for forming outer coating  8  by coating a surface of the conductive layer  4  with insulation resin  13;  and an electrode forming process for forming electrodes  9  at both ends of the coil portion  7,  and for making electric contacts between electrodes  9  and the conductive layer  4.  A chip inductor having a flattened mounting surface of the outer coating is obtained when insulation resin layer  8  is formed by an electrodeposition in the insulation resin coating process. The chip inductor can be securely mounted to a circuit board.

FIELD OF THE INVENTION

[0001] The present invention relates to a method of manufacturing chipinductor for use in a variety of consumer electronic equipment and thelike.

BACKGROUND OF THE INVENTION

[0002] With reference to the accompanying drawings, a conventionalmethod of manufacturing chip inductor will be described hereinafter.

[0003]FIG. 18 illustrates a conventional manufacturing process of a chipinductor, FIG. 19 is a cross sectional view of the chip inductor, andFIG. 20 is a perspective view of the chip inductor.

[0004] In FIG. 18 through FIG. 20, the conventional method ofmanufacturing the chip inductor comprises a first step of formingconductive layer 32 on rectangular prism substrate 31 made of insulatingmaterial of approximately 0.5 mm square by 1 mm in length, a second stepof forming coil portion 35 having spiral conductor 33 and groove 34 byslitting the conductive layer 32 spirally with laser 37, a third step offorming electrodes 36 at both ends of the coil portion 35, and a fourthstep of forming outer coating 39 by coating the coil portion 35 withinsulation resin 38, followed by heating.

[0005] In the fourth step, the coil portion 35 is coated on its entireperiphery with the insulation resin 38 by rolling the substrate 31 in adirection of (A) on a tape coated with the insulation resin 38.

[0006] Thereafter, the insulation resin 38 is heated to form the outercoating 39.

[0007] In the above-described method of the prior art, since theinsulation resin 38 is coated while rolling the substrate 31 on the tapecoated with the insulation resin 38, an external shape of the insulationresin 38 enclosing the prism substrate 31 becomes cylindrical, as shownin the cross sectional view of FIG. 19, due to its surface tension.

[0008] The chip inductor is especially susceptible to an influence ofsurface tension of the insulation resin 38, because of very smallexternal dimensions of its main body, which is approximately 0.5 mmsquare by 1 mm in length.

[0009] This causes a surface of the outer coating 39 to become round,thereby giving rise to a problem that it can not be mounted properly toa circuit board or the like as it rotates when it is mounted.

[0010] The present invention addresses the above-described problem, andis intended to provide a method of manufacturing chip inductor thatmakes a mounting surface of the outer coating flat, so as to assurereliable mounting.

SUMMARY OF THE INVENTION

[0011] In a manufacturing process of chip inductor, the presentinvention comprises an electrodeposition coating process, in which anelement main body having a coil portion formed thereon is dipped into abath for electrodepositing a insulation resin, and an electric field isapplied between a conductor of the coil and the resin bath, to cover thecoil with the resin by depositing the electrodeposition insulation resinat least on a surface of the conductor of the coil.

[0012] The above-described method covers the coil with theelectrodeposition insulation resin, instead of coating it with aninsulation resin, thereby avoiding an external shape of outer coatingfrom becoming round due to surface tension of the insulation resin, evenif external dimensions of the chip inductor are considerably small.Therefore, this produces an external shape that generally resemble to anexternal shape of a conductive layer, so as to make the outer coatingflat, and to improve easiness of mounting of the chip inductor to acircuit board or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIGS. 1(a) to 1(f) illustrate a manufacturing process of chipinductor according to a first exemplary embodiment of the presentinvention;

[0014] FIGS. 2(a) to 2(c) illustrate an electrodeposition coatingprocess of the chip inductor;

[0015] FIGS. 3(a) to 3(c) illustrate a heating process of the chipinductor;

[0016]FIG. 4 is a sectional view of the chip inductor;

[0017]FIG. 5 is a perspective view of the chip inductor;

[0018] FIGS. 6(a) to 6(d) illustrate an electrode forming process of achip inductor according to a second exemplary embodiment of the presentinvention;

[0019]FIG. 7 is a sectional view of the chip inductor;

[0020]FIG. 8 is a perspective view of the chip inductor;

[0021]FIG. 9 is a sectional view of another chip inductor according tothe second exemplary embodiment of the present invention;

[0022]FIG. 10 is a sectional view of a chip inductor according to athird exemplary embodiment of the present invention;

[0023]FIG. 11 is a sectional view of the chip inductor;

[0024]FIG. 12 is a perspective view of the chip inductor;

[0025]FIG. 13 is a sectional view of another chip inductor according tothe third exemplary embodiment of the present invention;

[0026] FIGS. 14(a) to 14(c) illustrate an etching process of a chipinductor according to a fourth exemplary embodiment of the presentinvention;

[0027] FIGS. 15(a) and 15(b) illustrate a process of forming an oxidefilm of the chip inductor;

[0028]FIG. 16 is a sectional view of the chip inductor;

[0029]FIG. 17 is a perspective view of the chip inductor;

[0030] FIGS. 18(a) to 18(d) illustrate a manufacturing process of a chipinductor of the prior art;

[0031]FIG. 19 is a sectional view of the prior art chip inductor; and

[0032]FIG. 20 is a perspective view of the prior art chip inductor.

THE BEST MODE FOR CARRYING OUT THE INVENTION First Exemplary Embodiment

[0033] With reference to the accompanying drawings, the presentinvention as set forth in claims 1 through claim 9 is describedaccording to the exemplary embodiment.

[0034] Referring to FIG. 1 though FIG. 5, a method of manufacturing chipinductor according to this exemplary embodiment of the inventioncomprises:

[0035] a conductive layer forming process for forming conductive layer 4on outer periphery 2 and end surfaces 3 of substrate 1 made ofinsulating material having a prism shape of approximately 0.5 mm squareby 1 mm in length;

[0036] a coil portion forming process for forming coil portion 7 havingconductor 5 and groove 6 by cutting spirally the conductive layer 4formed on the outer periphery 2 of the substrate 1 while removingcutting dust 10 of the conductive layer 4;

[0037] an etching process for etching the chip inductor element havingthe coil portion 7 formed thereon;

[0038] an insulation resin coating process for forming outer coating 8by coating the outer periphery 2 and the conductive layer 4 of theetched element with insulation resin 13;

[0039] and an electrode forming process for forming electrodes 9 at bothends of the coil portion 7, and for making electrical contacts betweenthe electrodes 9 and the conductive layer 4.

[0040] Furthermore, in the insulation resin coating process, thesubstrate 1 having the coil portion 7 formed thereon is dipped intoepoxy-based insulation resin bath 11 for electrodeposition while beinghold by holder 14, and an electric field is applied between theconductor 5 of the coil portion 7 and the resin bath 11, as shown inFIG. 2. The electric field is applied by power supply 12 connectedbetween electrode plate 15 and the holder 14. Application of theelectric field causes the electrodeposition insulation resin to depositon at least a surface of the conductor 5, to cover the coil portion 7 asinsulation resin 13. As described, the insulation resin coating processincludes an electrodeposition process. Electrophoretic resin generallyavailable on the market can be used as the electrodeposition resin.

[0041] In the electrodeposition process, surfaces of the conductivelayer 4 formed on the both end surfaces 3 of the substrate 1 are notexposed to the electrodeposition insulation resin in the resin bath 11,as shown in FIG. 2(b), so as not to be coated with the insulation resin13. In addition, there is provided an electric-field controlling processto cease application of the electric field before thickness (W1) of theinsulation resin 13 covering the coil portion 7 become greater thanthickness (W2) of the conductive layer 4, as shown in FIG. 2(c).

[0042] Furthermore, there are cleaning process for washing theinsulation resin 13, after the electrodeposition process, as well asheating process, thereafter, for heating the insulation resin 13 tocure.

[0043] In the heating process, the insulation resin 13 is heated at atemperature lower than its curing temperature, and then at anothertemperature higher than the curing temperature of the resin to cure theinsulation resin 13.

[0044] More specifically, in the heating process, the insulation resin13 is heated at a temperature (130° C.) that is lower than the curingtemperature to allow the insulation resin 13 to flow and to fill grooves6 in the coil portion 7, as shown in FIG. 3(b). The insulation resin 13is then heated at a temperature (230° C.) higher than the curingtemperature to form a continuous layer of the insulation resin, as shownin FIG. 3(c).

[0045] According to the foregoing method, the insulation resin 13 is notformed by a coating method, but the electrodeposition insulation resinis deposited only on the conductor 5, and cover the entire coil portion7. Thus, an amount of the coated insulation resin 13 can be controlledaccurately as described above, so as to avoid an external shape of theouter coating 8 from becoming round due to surface tension of theinsulation resin 13, even if external dimensions of the substrate 1 aresubstantially small. In other words, an external shape of the chipinductor becomes what is generally the same to an external shape of theconductive layer 4, thereby making the outer coating 8 flat, andimproving easiness of mounting it to a circuit board or the like.

[0046] In particular, since there is the electric-field controllingprocess provided in the electrodeposition process to cease applicationof the electric field before the thickness of the insulation resin 13becomes greater than thickness of the conductive layer 4, the chipinductor can be miniaturized by reducing the thickness of the insulationresin 13. This makes the external shape of the insulation resin 13 to bethe same more accurately to the external shape of the conductive layer4, so as to further improve flatness of the mounting surface.

[0047] In the electrodeposition process, surfaces of the conductivelayer 4 formed on both end surfaces 3 of the substrate 1 are notdeposited with the insulation resin 13. This allows electrical contactsbetween electrodes 9 and the conductive layers 4 when the electrodes 9are formed at both ends of the coil portion 7. In addition, it alsoimproves reliability of contacts, since surface area of the contactsbetween the electrodes 9 and the conductive layers 4 can be very large,as shown in FIG. 4.

[0048] Furthermore, because there is also the heating process forheating and curing the insulation resin 13 after the electrodepositionprocess, the outer coating can be formed adequately by curing theinsulation resin 13 after the coil portion 7 is covered with theinsulation resin 13.

[0049] In the heating process, the insulation resin 13 is heated at thetemperature lower than the curing temperature, and thereafter, atanother temperature higher than the curing temperature of the insulationresin 13. Therefore, the insulation resin 13 deposited to the conductors5 fills the grooves 6 between adjoining conductors 5 due to its flowproperty when it is heated at the lower temperature than the curingtemperature of the insulation resin 13. Thus, flat surface of theinsulation resin 13 is obtained, and a mounting procedure becomes easy.

[0050] The insulation resin 13 covering the coil portion 7 securelyfills the grooves 6 between the conductors 5 by the flow property of theinsulation resin 13. Because the insulation resin 13 is heated at thehigher temperature than the curing temperature of the insulation resin13, especially after the insulation resin 13 fill the grooves 6 of thecoil portion 7, a formation of voids in the grooves 6 can be prevented.

[0051] Accordingly, short-circuiting between adjoining conductors 5 andcorrosion and the like of the conductors 5 due to an invading ofmoisture or the like into the grooves 6 are eliminated, and thereliability becomes improved.

[0052] Also, because the cleaning process for cleaning the insulationresin 13 is included prior to the heating process, resin bath 11 simplyadhering to the substrate 1 after it is dipped into the resin bath 11 inthe insulation resin coating process can be washed out in the cleaningprocess. This further improves flatness of the outer coating 8, since iteliminates excess amount of electrodeposition insulation resin to flowand cure, and only the insulation resin 13 deposited on the conductors 5of the substrate 1cures.

[0053] Since the insulation resin specifically used for theelectrodeposition is epoxy-based resin, it is easily deposited on theconductors 5.

[0054] According to the present exemplary embodiment, as describedabove, flatness of the outer coating 8 is obtained, and the mounting ofthe chip inductor to a mount board and the like becomes easy.

[0055] Moreover, since large area electrical contacts are made betweenthe electrodes 9 and the conductive layers 4 without the outer coating 8in between, it improves reliability of the contacts.

[0056] In addition, since the insulation resin 13 heated at the lowertemperature than the curing temperature securely fills the grooves 6, iteliminates short-circuiting between the adjoining conductors 5 andcorrosion of the conductors 5, so as to improve the reliability. A goodresult was obtained for the resin used in this exemplary embodimentespecially when the lower temperature than the curing temperature wasset at 130° C. and the higher temperature at 230° C. However, thesetemperatures are changed, naturally, depending on a kind of the resinand curing agent used.

[0057] In this exemplary embodiment, although the grooves 6 in the coilportion 7 are not cut into a body of substrate 1, the grooves may be cutinto the body of substrate 1.

Second Exemplary Embodiment

[0058] With reference to the accompanying drawings, the presentinvention as set forth in claims 11 through claim 19 will be describedhereinafter according to the exemplary embodiment.

[0059] A method of manufacturing chip inductor in the second exemplaryembodiment is a further improvement of the first exemplary embodiment.

[0060]FIG. 6(a) through 6(d) illustrate an electrode forming process ofthe chip inductor according to the present exemplary embodiment, FIG. 7is a sectional view of the chip inductor, and FIG. 8 is a perspectiveview of the chip inductor.

[0061] In this exemplary embodiment, detailed descriptions are omittedup to the electrodeposition coating process, as they are the same asthose in FIG. 1 and FIG. 2 in the first exemplary embodiment.

[0062] In the electrode forming process of this embodiment includes aprocess of forming electrodes 9 on outer coating 8 over conductive layer4 formed on outer periphery 2 of the substrate 1. In the electrodeforming process, the electrodes 9 are formed in a manner that conductiveresin 16 is coated on parts of the conductive layers 4 formed on the endsurfaces 3, and the coated surfaces are flattened thereafter by aflattening plate 17 pressed thereon, as shown in FIGS. 6(a) and 6(b),followed by a curing of the conductive resin 16.

[0063] In addition, each electrode 9 is so formed that thickness (W1) ofthe electrode 9 formed around the outer periphery 2 of the substrate 1is less than thickness (W2) of the outer coating 8 formed over the outerperiphery 2 of the substrate 1, as shown in FIG. 7.

[0064] The electrode 9 is formed on the outer coating 8 from the endsurface 3 extending at least to a position (W3) that faces conductor 5.And, in particular, the width (W3) of the electrodes 9 formed over theouter periphery 2 of the substrate 1 is larger than ⅙ (W4) of a lengthof the substrate 1 but smaller than a half (W5) of the length.

[0065] According to the method of manufacturing of this embodiment, thefollowing advantages are obtained, in addition to the advantages of thefirst exemplary embodiment. That is, the electrodes 9 can be formed onthe outer coating 8, even if the conductors 5 are provided over anentire surface of the outer periphery 2 of the substrate 1, since theelectrodes 9 are formed over the conductive layers 4 with outer coating8 in between. In the foregoing manner, this embodiment provides thepossibility of increasing a coil area even with the same size of thesubstrate is used, thereby allowing an increase in inductance whilerealizing miniaturization at the same time.

[0066] Especially, since the electrodes 9 are provided on the outerperiphery of the substrate 1, the Manhattan phenomenon (a phenomenon inwhich one end of a chip component lift up, and a connection between thecircuit board and any of the electrodes 9 fails) during soldering to acircuit board can be eliminated, thereby improving reliability of themounting.

[0067] Furthermore, since there is a process of forming the conductivelayers 4 on both end surfaces 3 of the substrate 1, the electrodes 9 canbe formed also on the both end surfaces 3 of the substrate 1. Thisfurther improves a mounting reliability.

[0068] The electrodes 9 are formed especially in such a configurationthat thickness of the electrodes 9 formed on the outer periphery 2 ofthe substrate 1 is thinner than the thickness of the outer coating 8formed on the outer periphery 2 of the substrate 1. This eliminates apeeling-off of the electrodes 9 while attaining a low-profile structure,even when the electrodes 9 are formed over the outer coating 8, so as toimprove reliability.

[0069] The electrodes 9 can be formed precisely, since they are formedin the manner that conductive resin 16 is coated and cured. In addition,because the conductive resin 16 is cured after it is coated and thecoated surface is flattened by being pressed against flattening plate17, the mounting surface of the electrodes 9 can be made flat to improveeasiness of mounting.

[0070] The width (W3) of the electrodes 9 is so arranged that it islarger than ⅙ (W4) of a width of the outer periphery of the substrate 1but smaller than a half (W5) of the substrate 1. This securelyeliminates the Manhattan phenomenon during soldering of the electrodes 9to the circuit board and the like, thereby improving the connectionreliability.

[0071] According to the second embodiment of the present invention, inaddition to the advantage of the first embodiment, there are suchadvantages as an increase in inductance while realizing miniaturization,and an improvement in connection reliability. In addition, it alsoavoids the electrodes 9 from the peeling-off, so as to also improve thereliability.

[0072] According to the second embodiment of the present invention, theelectrodes 9 are formed from the end surfaces 3 of the substrate 1 up toat least the positions where each faces their respective conductor 5, inthe electrode forming process. However, the electrodes 9 may be formedin a manner that they locate between the end surfaces 3 of the substrate1 to the conductor 5. In other words, the outer coating 8 is removedpartly or entirely, and the electrodes 9 are connected to the conductivelayer 4 at the removed area. The peeling-off of the electrodes 9 can besuppressed in this case, as compared to the case in which the electrodes9 are formed over the outer coating 8. Well known means such as laserbeam stripping, machine cutting, and the like can be used for theremoval of the outer coating 8.

[0073] In addition, although the conductive layer 4 is formed on bothend surfaces 3 of the substrate 1 in the conductive layer formingprocess of the present invention, a process may be employed that doesnot form the conductive layer 4 on the both end surfaces 3 of thesubstrate 1, leaving these surfaces not coated with conductive-layer, asshown in FIG. 9. In this instance, the inductance can be increased whileachieving miniaturization, since there is no conductive substance on theend surfaces 3 of the substrate 1 to shield magnetic flux generated bythe coil portion 7. The conductive layer 4 and the electrodes 9 can beconnected even in this case by removing the outer coating 8 partially orentirely.

[0074] Alternatively, the holder 14 shown in FIG. 2 may be made of aconductive elastic member, to produce non-deposited areas where theouter coating 8 is not formed at the ends of the conductive layer 4.

Third Exemplary Embodiment

[0075] Referring now to the accompanying drawings, the invention as setforth in claims 20 through claim 25 will be described hereinafteraccording to this exemplary embodiment.

[0076] A method of manufacturing chip inductor in this exemplaryembodiment is a further improvement of the method of manufacturing thechip inductor of the first exemplary embodiment.

[0077] FIGS. 10(a) and 10(b) are sectional views of chip inductorsaccording to the third exemplary embodiment of the present invention,FIG. 11 is a sectional view of another chip inductor, and FIG. 12 is aperspective view of the chip inductor.

[0078] Detailed descriptions are omitted up to the electrodepositioncoating process, as they are same as those in FIG. 1 and FIG. 2 in thefirst exemplary embodiment. According to the present exemplaryembodiment, a process is provided to form conductive layers 4 on bothend surfaces 3 of the substrate 1, in the conductive layer formingprocess. There is also another process, in the electrode formingprocess, to cut surfaces of the conductive layers 4 formed on the bothend surfaces 3 of the substrate 1.

[0079] In the electrode forming process, the laser beam is scanned for aplurality of times to cut the surfaces of the conductive layers 4 formedon the both end surfaces 3 of the substrate 1. A cutting depth to cutthe surfaces of the conductive layers 4 is an extent that does notexpose the both end surfaces 3 of the substrate 1.

[0080] The following advantages can be obtained according to theforegoing method, in addition to the advantages of the first exemplaryembodiment as shown in FIGS. 10(a) and 10(b). That is, since the processincludes cutting process of the surfaces of the conductive layers 4formed on the both end surfaces 3 of the substrate 1, the insulationresin 13 can be removed by the cutting, as shown in FIG. 10(b), even ifthe conductive layers 4 formed on the end surfaces 3 is covered with theinsulation resin 13, as shows in FIG. 10(a). The insulation resin 13flows over the end surfaces 3 when the electrodeposition insulationresin is deposited to the surface of the conductor 5 of the coil portion7.

[0081] As a result, it is not likely that electrical contacts betweenthe electrodes 9 and the conductive layers 4 are deteriorated, and thatshape of the electrodes 9 becomes large due to the deposited insulationresin 13. It therefore improves connection reliability of theelectrodes, and achieves downsizing of the chip inductor.

[0082] Since the cutting depth to cut the surfaces of the conductivelayers 4 formed on the both end surfaces 3 is set to the extent not toexpose the both end surfaces 3 of the substrate 1, a connectionreliability between the conductive layers 4 and the electrodes 9 on theboth end surfaces 3 when forming the electrodes 9 on the end surfaces 3of the substrate 1 is improved.

[0083] Specifically, since surfaces of the conductive layers 4 formed onthe both end surfaces 3 are cut by a plurality of laser beam scanning,the surfaces of the conductive layers 4 can be surely cut, therebyresulting in an improvement of connection reliability.

[0084] According to the third exemplary embodiment of the presentinvention, as described above, an external shape of the outer coating 8never becomes round due to surface tension of the insulation resin 13even if external dimensions are considerably small. And, it becomes sucha shape that is generally the same with an external shape of theconductive layer 4, thereby making the outer coating 8 flat, andimproving easiness of mounting to a circuit board or the like.

[0085] It also improves connection reliability of the electrodes 9 tothe conductive layers 4 formed on the both end surfaces 3 of thesubstrate 1, while achieving miniaturization at the same time.

[0086] According to this exemplary embodiment, the surfaces of theconductive layers 4 formed on the both end surfaces 3 of the substrate 1are cut with laser irradiation in the electrode forming process.However, surfaces of the conductive layers 4 formed at edges of theouter periphery 2 of the substrate 1 may also be cut, as shown in FIG.13, with the laser irradiation. This method can result in furtherimprovement in connection reliability of the electrodes 9 to theconductive layers 4.

Fourth Exemplary Embodiment

[0087] Referring now to the accompanying drawings, the invention as setforth in claims 26 through claim 32 will be described hereinafteraccording to this exemplary embodiment.

[0088] A method of manufacturing chip inductor in the fourth exemplaryembodiment is another improvement to the method of manufacturing thechip inductor of the first exemplary embodiment.

[0089] FIGS. 14(a) through 14(c) illustrate an etching process of chipinductor in the manufacturing process according to the fourth embodimentof the present invention, FIG. 15 illustrates a process showingformation of an oxide film in the manufacturing process of the chipinductor, FIG. 16 is a sectional view of the chip inductor, and FIG. 17is a perspective view of the chip inductor. Detailed descriptions areomitted for the general manufacturing process and the electrodepositioncoating process shown in FIG. 1 and FIG. 2, as they are same as those ofthe first exemplary embodiment.

[0090] In this exemplary embodiment, an etching process is provided asshown in FIGS. 14(a) through 14(c), wherein a chip inductor element,which has a groove by laser irradiation, is dipped into electrolyticsolution 19, electric field is applied between conductive layer 4 andthe electrolytic solution 19 with power supply 21 connected to a pair ofelectrode plates 20, and the element is electrolytically etched so thatthickness (W2) of the conductive layer 4 becomes larger than width (W1)of conductor 5 of the coil portion 7.

[0091] In this etching process, the element is etched electrolyticallyin a manner that substrate 1 formed with conductive layer 4 is placed invessel 22, one of the electrode plate 20 is inserted in the vessel 22,and electric field is applied between the conductive layer 4 and theelectrolytic solution 19 through the pair of electrode plates 20 whilethe substrate 1 is kept in contact with the electrode plate 20.

[0092] Another process is provided, after the etching process, to formoxide film 23 over the conductor 5 of the coil portion 7, as shown inFIG. 15(b).

[0093] The following advantages are obtained through the above method,in addition to those obtained in the first exemplary embodiment.

[0094] It is that, cutting dust 10 produced during groove-cuttingprocess of the conductive layer 4 can be removed, even if they remainfirmly attached to surface of the conductive layer 4 and in grooves 6 ofthe substrate 1, since the substrate 1, after cutting with laser, isetched electrolytically.

[0095] As a result, it avoids adjoining conductors 5 fromshort-circuiting therebetween, and a film of the insulation resin 13from becoming not uniform in the insulation resin coating process, andthereby the reliability can be improved.

[0096] Moreover, because the element is etched electrolytically byapplying electric field between the conductive layer 4 of the substrate1 and the electrolytic solution 19, while the element is placed in thevessel 22 and kept in contact with the electrode plate 20, it ispossible to circulate the electrolytic solution 19 in contact with theconductive layer 4 efficiently for carrying out the etchingsuccessfully.

[0097] The etching process is specially provided so as to make thickness(W2) of the conductive layer 4 larger than width (W1) of the conductor 5of the coil portion 7. This eliminates a reduction in inductance becausea surface area of the conductor 5 does not decrease even when a numberof turns of the conductor 5 is increased, thereby improving reliability.

[0098] In addition, there is provided a process of forming oxide film 23on the conductor 5 after the etching process, which improves adhesion ofthe electrodeposited insulation resin 13 to the conductor 5.Consequently, it prevents peeling-off between the insulation resin 13and the conductor 5, so as to positively avoid corrosion, disconnection,and the like of the coil. Moreover, there are cases, depending on kindof the electrodeposition resin, in which deposition of the insulationresin for electrodeposition on the surface of conductor 5 of the coilportion 7 can be facilitated by forming the oxide film 23. In general, ahighly conductive material such as copper is used for the conductor 5.Since oxide layer of such material has electrical conductivity, it isunlikely that presence of the oxide layer prevents theelectrodeposition.

[0099] In addition to the advantages of the first exemplary embodiment,the fourth exemplary embodiment of the present invention, as described,prevents adjoining conductors 5 from short-circuiting therebetween, anda film of the insulation resin 13 from becoming not uniform in theinsulation resin coating process, and thereby the reliability isimproved.

[0100] In this exemplary embodiment, the electrolytic etching processwas disclosed. However, the same result is obtained even with a chemicaletching process that uses acidic solution, in place of the electrolyticetching process.

[0101] And, when the element formed with the conductive layer 4 ischemically etched while being vibrated with ultrasonic wave, acidicsolution in contact with the conductive layer 4 can be circulatedefficiently, to successfully carry out the etching.

[0102] However, the electrolytic etching can shorten etching time, andis easy to control a degree of etching, and is capable of etching moreprecisely.

[0103] Furthermore, in the etching process of the fourth exemplaryembodiment of the present invention, a process is provided, in which thesubstrate 1 is electrolytically etched so that the thickness (W2) of theconductive layer 4 becomes larger than the width (W1) of the conductor 5of the coil portion 7. However, it is also acceptable to make thethickness (W2) of the conductive layer 4 smaller than the width (W1) ofthe conductor 5.

Industrial Applicability

[0104] According to the present invention, as described above, there isrealized a chip inductor having an external shape that is generally thesame with an external shape of conductive layer, since the externalshape of its outer coating never becomes round due to surface tension ofthe insulation resin even if external dimensions of it are significantlysmall. Consequently, this can provide a method of manufacturing the chipinductor which makes the outer coating 8 flat, and improve easiness ofmounting to a circuit board or the like.

What is claimed is:
 1. A method of manufacturing chip inductorcomprising: a process of forming a conductive layer on an outerperiphery of a substrate made of insulating material; a coil portionforming process for forming a coil by spirally cutting said conductivelayer; an etching process for etching said coil; an insulation resincoating process for forming an outer coating by coating at least saidcoil on said substrate with insulation resin; and an electrode formingprocess for forming an electrode at both ends of said coil, and formaking an electric contact between said electrode and said conductivelayer, wherein said insulation resin coating process includes anelectrodeposition process for covering said coil with said insulationresin, using electrodeposition method to deposit said electrodepositioninsulation resin at least on a surface of a conductor of said coil. 2.The method of manufacturing chip inductor according to claim 1, furthercomprising a heating process for heating and curing said insulationresin, after said electrodeposition process.
 3. The method ofmanufacturing chip inductor according to claim 2, further comprising acleaning process prior to said heating process.
 4. The method ofmanufacturing chip inductor according to claim 2, wherein said heatingprocess comprises a first heating process for heating said insulationresin at a temperature lower than a curing temperature of saidinsulation resin, and a second heating process for heating saidinsulation resin thereafter at a temperature higher than the curingtemperature of said insulation resin.
 5. The method of manufacturingchip inductor according to claim 2, wherein said heating processcomprises a heating and filling process for heating said insulationresin at a temperature lower than a curing temperature of saidinsulation resin for filling a groove in said coil portion with saidinsulation resin, and a second heating process for heating saidinsulation resin at a temperature higher than the curing temperature ofsaid insulation resin for curing said insulation resin.
 6. The method ofmanufacturing chip inductor according to claim 4, wherein said firstheating process is carried out at 130° C., and said second heatingprocess is carried out at 230° C.
 7. The method of manufacturing chipinductor according to claim 5, wherein said heating and filling processis carried out at 130° C., and said second heating process is carriedout at 230° C.
 8. The method of manufacturing chip inductor according toclaim 1, wherein surfaces of said conductive layer formed on both endsurfaces of said substrate are not in contact with an electrodepositionbath to maintain said surfaces free of deposition of said insulationresin.
 9. The method of manufacturing chip inductor according to claim 1further including an electric-field controlling process in saidelectrodeposition process, wherein said electric-field controllingprocess ceases application of electric field before a thickness of saidinsulation resin covering said coil becomes greater than a thickness ofsaid conductive layer formed on the outer periphery of said substrate.10. The method of manufacturing chip inductor according to claim 1wherein said electrodeposition insulation resin is epoxy-based resin.11. The method of manufacturing chip inductor according to claim 1further including in said electrode forming process, a process offorming said electrode on said conductive layer formed on the outerperiphery of said substrate with said insulation resin in between. 12.The method of manufacturing chip inductor according to claim 11 furtherincluding in said electrode forming process, a process of forming saidelectrode from an end surface of said substrate to at least a portionthat faces said conductor with said insulation resin in between.
 13. Themethod of manufacturing chip inductor according to claim 11 furtherincluding in said electrode forming process, a process of forming saidelectrode in a manner to locate between an end surface of said substrateand said conductor that constitutes said coil.
 14. The method ofmanufacturing chip inductor according to claim 11 further including insaid conductive layer forming process, a process of forming a conductivelayer also on both end surfaces of said substrate, and a process offorming an electrode on said conductive layer formed on the end surfaceof said substrate.
 15. The method of manufacturing chip inductoraccording to claim 11 including in said conductive layer formingprocess, a process of leaving portions free of conductive layer by notforming said conductive layer on both end surfaces of said substrate,and a process of leaving portions free of electrode by not forming saidelectrode on said end surfaces of said substrate.
 16. The method ofmanufacturing chip inductor according to claim 11 further including insaid electrode forming process, a process of forming said electrode in amanner that a thickness of said electrode formed on the outer peripheryof said substrate is smaller than a thickness of said insulation resinformed on the outer periphery of said substrate.
 17. The method ofmanufacturing chip inductor according to claim 11 further including insaid electrode forming process a process of forming said electrode bycoating conductive resin and curing said conductive resin.
 18. Themethod of manufacturing chip inductor according to claim 11 furtherincluding in said electrode forming process a process of forming saidelectrode by coating conductive resin, flattening a coated surface bypressing it against a flattening plate after said conductive resin iscoated, and curing said conductive resin thereafter.
 19. The method ofmanufacturing chip inductor according to claim 11, wherein saidelectrode is formed in said electrode forming process in such aconfiguration that a length of said electrode located on the outerperiphery of said substrate is larger than ⅙, but smaller than ½ of adimension of said substrate, both said length and said dimension beingtaken along an axial direction of said coil.
 20. The method ofmanufacturing chip inductor according to claim 1, wherein saidconductive layer is formed on both end surfaces of said substrate, andsaid method further includes in said electrode forming process a processof cutting a surface of said conductive layer formed on the both endsurfaces of said substrate.
 21. The method of manufacturing chipinductor according to claim 20, wherein in said electrode formingprocess, a cutting depth to cut the surface of said conductive layerformed on the both end surfaces of said substrate is set to an extentnot to expose the both end surfaces of said substrate.
 22. The method ofmanufacturing chip inductor according to claim 20, wherein in saidelectrode forming process, the surface of said conductive layer formedon the both end surfaces of said substrate is cut with a laserirradiation.
 23. The method of manufacturing chip inductor according toclaim 22, wherein said laser irradiation is performed by scanning thesurface of said conductive layer for a plurality of times.
 24. Themethod of manufacturing chip inductor according to claim 20, wherein insaid electrode forming process, the surface of said conductive layerformed on the both end surfaces of said substrate and the surface ofsaid conductive layer formed on an end portion of said outer peripheryof said substrate are cut with laser irradiation.
 25. The method ofmanufacturing chip inductor according to claim 24, wherein said laserirradiation is performed by scanning the surface of said conductivelayer for a plurality of times.
 26. The method of manufacturing chipinductor according to claim 1 wherein said etching process includes aprocess of electrolytic etching with application of electric fieldbetween said conductive layer on the surface of said substrate and theelectrolytic solution.
 27. The method of manufacturing chip inductoraccording to claim 26 further comprising a process of forming an oxidefilm on the conductor of said coil on said substrate, after said etchingprocess.
 28. The method of manufacturing chip inductor according toclaim 26, wherein electrolytic etching is carried out in said etchingprocess while said conductive layer is kept in contact with an electrodeplate for application of electric field.
 29. The method of manufacturingchip inductor according to claim 26, wherein electrolytic etching iscarried out in said etching process, in a manner that said substratehaving said conductive layer formed thereon is placed in an electricallyconductive vessel, electric field is applied between said conductivelayer and electrolytic solution through said vessel while said substrateis kept in contact with said vessel.
 30. The method of manufacturingchip inductor according to claim 26, wherein electrolytic etching iscarried out in said etching process so that a thickness of saidconductive layer becomes larger than a width of the conductor of saidcoil.
 31. The method of manufacturing chip inductor according to claim1, wherein said etching process is a chemical etching process.
 32. Themethod of manufacturing chip inductor according to claim 1, wherein saidetching process is a chemical etching process with ultrasonic vibration.